1. Field of the Invention
The invention relates to a Coriolis mass flowmeter with a measuring tube that can have a medium flowing through it, with at least one actuator and with at least one sensor, wherein the measuring tube is bent between its input end and its output end into a first winding and a second winding, the first winding and the second winding merging into one another at a transitional section of the measuring tube, the first winding and the second winding running in parallel winding planes and being opposite one another and wherein the first winding and the second winding can be excited to oscillation in oscillating sections by the actuator and the oscillations can be detected by the sensor.
2. Description of Related Art
Coriolis mass flowmeters have been known in a variety of very different designs for many years. In mass flowmeters that are based on the Coriolis principle, a measuring tube with medium flowing through it or measuring tubes with a medium flowing through them is/are excited to oscillation by an actuator, which preferably corresponds to an eigenfrequency of the measuring tube in the mounted position. On the input side and output side, inertial forces act differently on the flowing medium in the measuring tube excited to oscillation, and thus, on the measuring tube itself, so that the deflection of the measuring tube is influenced differently on the input and output sides. Usually, two sensors are provided for detecting oscillations, spaced from the actuator on the input and output sides so that, overall, the oscillations of the measuring tube detected by the sensors on the input and output sides have a phase shift that is a direct measure of the mass flow of interest. The measurement, namely the mass flow, is derived from the phase shift using evaluation electronics.
Such Coriolis mass flowmeters have the advantage that they only use one measuring tube, however, the measuring tube is bent into a first winding and a second winding that are opposite one another, i.e., run practically parallel to one another. The actuator acting between the first winding and the second winding deflects the oscillating sections of the first winding and the second winding in opposite directions—i.e., going away from or toward each other—so that the center of mass of the system is maintained overall and external oscillations, i.e., from connections, are practically not noticeable. This advantage is achieved by other Coriolis mass flowmeters that have more than one measuring tube and in which these measuring tubes are correspondingly deflected, however, in Coriolis mass flowmeters having more than one measuring tube, there has to be a transitional section (flow divider) on the input and output sides between a process connection and the multiple measuring tubes, which is omitted in the solution with one measuring tube wound into parallel loops.
When a Coriolis mass flowmeter is built into a piping system, external oscillations—should there be any—are inevitably transferred to the measuring device, which can negatively influence the measurement results because the measurement results are based directly on the oscillations detected by the sensors.
In particular, in small Coriolis mass flowmeters that are provided for the measurement of very small flow amounts, such a coupling of external oscillations is a problem.